<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <title>Document</title>
</head>

<body>
    <div class="wrap">
        <div id="header">
            header
        </div>
        <div id="content">

            <!-- 中间盒子优先渲染 -->
            <div id="middle">
                <div class="middle-inner">
                    middle
                </div>
            </div>

            <div id="left">
                left
            </div>


            <div id="right">
                right
            </div>

        </div>

        <div id="footer">
            footer
        </div>
    </div>
</body>

</html>